(1) Field of the Invention
The present invention relates to the field of rotorcraft, and more particularly it relates to equipment on board rotorcraft for lighting the surrounding environment.
The present invention provides a rotorcraft having such equipment, comprising a plurality of devices for lighting respective zones for illumination that are remote from the rotorcraft. The present invention also provides such rotorcraft lighting equipment, and a method of operating it.
(2) Description of Related Art
Rotorcraft are fitted with various on-board devices for lighting the surrounding environment. In general terms, such lighting devices make use of one or more headlights, and of means for controlling the emission of a light beam by means of the or each headlight. The control means are suitable for being activated by an operator on board the rotorcraft, a pilot or a copilot, in particular. Activation of the control means by the operator depends on a control member operated by a human.
The organization and the positioning of headlights on the rotorcraft vary depending on constraints that are specific to the functions of the lighting devices. It is necessary to find a compromise between optimizing the function to which a lighting device is dedicated and the constraints that are associated with organizing and installing one or more headlights on the rotorcraft that are operated in order to perform the function. As an illustration, reference is made to a non-limiting list of types of lighting device that may be found on board rotorcraft, enabling a remote zone for illumination to be lighted, depending on the specific functions of the devices:
Landing lighting devices perform a function whereby the zone to be illuminated is a zone on which it is intended to land the rotorcraft. Landing lighting devices are for providing moderate lighting of a predetermined zone on the ground during an approach flight stage of the rotorcraft.
Searching lighting devices relate to an operator on board the rotorcraft observing the surrounding environment. Searching lighting devices are designed to light with strong illumination zones that may be relatively arbitrary and far away from the rotorcraft.
Winching lighting devices are designed to provide moderate lighting of a zone for illuminating that has previously been identified by the pilot using the searching lighting device. The zone for illuminating is larger than a zone for illuminating while landing, in order to make it possible to take action on the identified zone.
Amongst the constraints relating to organizing lighting devices, it is desirable for the cost of obtaining them to be as low as possible. The total weight of the set of headlights fitted to the rotorcraft must also be kept as small as possible. It is appropriate to limit the number of headlights fitted to the rotorcraft without diminishing the desired lighting functions. The equipment included individually in each of the headlights installed on the rotorcraft must be limited and of structure that is as simple as possible, without that impeding the operation of the various lighting devices with which they are respectively associated.
The arrangement and positioning of the headlights on the rotorcraft must be organized so as to avoid them generating drag to the detriment of the aerodynamic performance of the rotorcraft. It is thus common practice to mount a headlight retractably on a rotorcraft so as to enable it to be refracted while it is not in use, and/or to install a headlight on a rotorcraft in a zone that limits its wind resistance.
It is desirable to optimize the space available on the rotorcraft for installing equipment other than lighting devices. The location on the rotorcraft and the size of the headlights together with their equipment need to take account of optimizing available space. It is also necessary for the locations of the headlights on the rotorcraft and the ways in which they are installed to avoid interposed masks, i.e. obstacles to the passage of the light beams from the headlights to the remote zone that is to be illuminated.
The outside wall of the rotorcraft is formed by a skin that is fragile and needs to be protected. The power of the headlight is a determining factor in obtaining lighting of satisfactory brightness for the zone to be illuminated, depending on the function required of the lighting device. The lighting power of a headlight leads to it heating up, so that a compromise needs to be found between the power of the light beam that it emits and the effect of the heat that is given off on the skin of the rotorcraft. The thermal power of the headlight should be as small as possible and the location of the headlight and/or the way it is installed should avoid causing the outside wall of the rotorcraft to be heated.
Mounting the headlight movably on the rotorcraft obtains the advantage of making it retractable, or indeed of enabling it to be steered so as to point the light beam that it emits to almost any remote zone for illuminating. The movements of the headlight are preferably dependent on control means so as to enable the operator to point it as required. The control member is associated with control means formed by at least one computer for managing the operation of the headlight, both with regard to emitting the light beam that it emits and with regard to how it is pointed.
Landing lighting devices comprise one or more headlights that conventionally present moderate power, of about 250 watts (W). A headlight is mounted stationary on the rotorcraft and it is optionally accompanied by another headlight that is mounted to be movable. Winching lighting devices comprise a plurality of independent headlights, commonly two of them, and each of them conventionally has medium power of the order of 600 W. The headlights for winching lighting devices are preferably individually mounted to be movable on the rotorcraft so as to enable the pilot to point each of the respective light beams they emit in independent manner. Given their functions, there is limited freedom in selecting locations on the rotorcraft for the headlights making up lighting devices that are dedicated to landing and/or to winching. The overall size of the headlights should be limited as much as possible in order to make them easier to install on the rotorcraft, while avoiding the thermal effects they induce, and not impeding the installation of other pieces of equipment.
Lighting devices for searching are more complex and bulky than lighting devices dedicated to landing and winching. The searchlights need to light the zone for illuminating with light of strong intensity, by using powerful headlights that give rise to considerable heating. The lighting devices used for searching comprise one or more searchlights that are conventionally carried together by a frame. The searchlights are individually mounted on the frame via respective supports belonging to each of them. The frame and/or the support are potentially large with considerable bulk, e.g. being mounted on a mast, or the like. The frame is commonly mounted to be extractable from the rotorcraft, so as to limit the drawbacks associated with its considerable bulk and so as to avoid harmful wind resistance of the searchlights while the searching lighting device is not being used. Given that the locations of the zones for illuminating are potentially relatively arbitrary, the searchlights may easily be placed in temporary manner on the rotorcraft, while avoiding possible masking that might impede the passage of the light beams towards the zone for illuminating. Extending the frame and/or the support procures the advantage of moving the searchlight(s) away from the outside wall of the rotorcraft, thereby avoiding heating it as a result of the considerable power of each of the searchlights, which power is of the order of 1600 W. When a plurality of searchlights are mounted on the support, the searchlights are mounted to move together so as to enable them to be pointed together towards the zone for illuminating, while restricting their individual power levels, even though together they provide considerable illumination of the remote zone to be lighted.
For information about a technological environment that is close to that of the present invention, reference may be made for example to the documents WO 00/49331 (Allied Signal Inc.) and WO 03/039957 (Honeywell Int. Inc.), which describe searchlights on board rotorcraft that are dedicated to lighting a zone for illumination that is remote from the rotorcraft. Operation of those searchlights depends on control means that are dedicated to managing their operation.
Reference may also be made to document EP 1 138 593 (Hella KG Hueck & Co.), which describes a headlight including a landing lighting device. The headlight is mounted stationary on the aircraft and it is fitted with a gas discharge lamp and a plurality of optical systems. The optical systems are mounted to move together inside the headlight, so as to emit respective light beams that make it possible to illuminate the zone for illuminating in an overlapping configuration with sufficient light intensity, while limiting the thermal effects produced by the headlight.
Reference may also be made to the following documents: U.S. Pat. No. 3,634,622 (Wheeler B. A.); WO 00/49331 (Allied Signal Inc.); and U.S. Pat. No. 5,589,901 (Means K. P.), which describe various searching lighting devices having at least one searchlight movably mounted on a rotorcraft.
According to document U.S. Pat. No. 3,634,622 (Wheeler B. A.), a searching lighting device has two searchlights mounted to be individually movable on a rotorcraft. The searchlights may be steered to converge on a zone for illuminating that is remote from the rotorcraft.
According to document WO 00/49331 (Allied Signal, Inc.), a searchlight is movably mounted with motor drive on a rotorcraft to be movable about two intersecting axes, respectively in azimuth and in elevation relative to the rotorcraft. The searchlight is tiltable between a retracted position inside a housing formed in the wall of the rotorcraft, and a deployed position outside the housing. The searchlight when tilted into the deployed position is also steerable to pivot in turning.
According to document U.S. Pat. No. 5,589,901 (Means K. P.), a pair of searchlights are movable by using motorized means under the control of control means that can be activated by a human.
The ways in which lighting equipment of a rotorcraft are organized need to be improved, given the variety of potential functions involved when lighting a zone for illuminating that is remote from the rotorcraft.